1. Field of the Invention
The present invention relates in general to optical disk storage systems and more particularly, to a method and apparatus for providing adaptive control of track servo.
2. Description of the Related Art
In recent years, optical disk devices have been used to record or reproduce large amounts of data. Optical disks are storage mediums from which data is read and to which data is written by laser. Each optical disk can store a large amount of data, typically in the order of 6 gigabytes. Such optical disk devices are under active technical developments for achieving higher recording density.
Current rewritable optical disks include spiral-shaped groove tracks having concave and convex portions formed on the surface of a disk substrate. On the surface of the substrate, a thin film that includes a recording material as a component is attached. During fabrication of the disks, concave and convex portions (pits) are often formed on the recording surface, simultaneously with the formation of guide grooves for tracking control, so as to record address information of each sector.
Each track of the optical disk is irradiated with a light beam having a predetermined recording power, so as to form recording marks on the recording thin film. The portions irradiated with the light beam (i.e., the recording marks) have different optical characteristics (reflection characteristics) from the other portions of the recording thin film. Thus, the recorded information can be reproduced or read by irradiating the track with a predetermined reproduction power and detecting light reflected from the recording film.
Accurate reading of information recorded on such optical disks may be impaired due to the existence of defects such as fingerprints, black dots, scratches and interruptions. When such defects are encountered during the read process, the optical head may be directed to move to a different track. In particular, defects are detected by monitoring a change in the beam strength signal reflected off the disk. Although the read information corrupted by defects resulting from scratches and black dots are irrecoverable, defects resulting from fingerprints render noisy but meaningful data. If the defect is not properly processed and handled, the resulting tracking error signal will be erroneous. Upon reading the erroneous tracking error signal, the servo control will direct the optical head to move off the current track. As a result, system performance is unnecessarily compromised.
Accordingly, there is a need in the technology to overcome the aforementioned problems.